Size Scales for Ancient Coins

What Numismatists do when they just don't know....

Ancient numismatics is a science constantly under revision. While the coins we study have not changed in the last thousand (or two thousand) years, our understanding of them is constantly changing in keeping with new discoveries and new theories about the coins and the civilizations that produced them. As a modern science, the study of ancient numismatics dates back to the Renaissance when men of position considered it fashionable to collect the coins of the classical civilizations they admired. By this time, no one remained that knew first hand the identifications and names the ancient people applied to their coins. Except for a few casual mentions in ancient writings, all this had to be deduced from the coins themselves. Some obvious information came easily; other seemingly important matters have yet to be explained. A major item of interest that is not completely understood is the system of denominations used during the late Roman period.

The denominations of the first two centuries of the Roman Empire are well documented allowing collectors to call their coins by the original names familiar to the man on the street. In 214 AD, Caracalla (Marcus Aurelius Antoninus) issued a new denomination which, for lack of a better name, collectors have dubbed "Antoninianus" in his honor. This combined with the earlier denominations (denarius, sestertius, dupondius, as etc.) to serve the Empire until the coinage was reformed in its entirety by Diocletian in 294 AD. Now the trouble begins. The old antoninianus was replaced by a new series of coins which was soon replaced by a new series (smaller, lighter and more debased) which was soon replaced by yet another series. Weight standards and relationships between the various coins changed so often that it seems impossible that we will ever have a full grasp on the proper names and their values for each and every year between Diocletian and the reform of Anastasius in 498 AD that collectors use to mark the change from "Roman" to "Byzantine" coins.

During this period we have a few references that refer to coins by name. The problem is that we are not always certain which coin was the one mentioned. Students differ on the proper application of "Centenionalis" and "Majorina". Numismatists of the 19th century, realizing the problems caused by the gaps in their knowledge, invented an arbitrary scale to refer to the bronze (Latin AES) and billon coins of the period. "Billon" coins containing no more than 5% silver are not easily distinguished from those containing none at all and, for this purpose, are not separated from those with no silver content. This avoids errors and allows identifying coins by their actual size if not denomination. It also allows for the fact that some coins might have retained the same names while they lost a good percentage of their size as time, and inflation, progressed. The coin we call "follis" or "nummus" can be 23mm in diameter or 13mm depending on the year it was issued. From a collector's standpoint it is nice to know which we are buying.

The "AE" scale divides all bronze (AES) coins into four groups by size. Coins over 25mm are called AE1. Those between 21mm and 25mm are AE2. Between 17mm and 21mm are AE3. Coins under 17mm are AE4. Coins not perfectly round are measured at their greatest diameter. With a little practice collectors can recognize these size groups easily without resorting to a ruler. The system works pretty well except for a few coin issues of the late 330's that vary from large AE4 to small AE3 sizes and are sometimes called AE3/4. The AE scale means absolutely nothing other than to define the size of the coins. For example, our AE1's of Diocletian and Valentinian I are both over 25mm but may have represented greatly different values in terms of buying power and completely different relationships between themselves and smaller bronzes or the gold coins of their day.

The AE1 to AE4 scale works ONLY for late Roman bronzes. Greek and Greek Imperial coins (bottom row in the photo and often equally mysterious when it comes to the names of the denominations) are measured by a completely different system. These are simply the measurement in millimeters preceded by the metal abbreviation. AE13, then, is a bronze coin of 13mm diameter; AR6 is a silver coin of 6mm diameter. Gold, Electrum, Nickel, Billon (looking a little silver) and Lead coins are abbreviated AV, EL, NI, BI and PB respectively. In both systems no effort is made to separate bronzes into copper, brass or other alloys; all are AE. The existence of this double system is made less confusing by the absence of late Roman Bronze coins as small as 4mm. If you see a coin called AE4 (or less) you know that it is measured by the late Roman scale. If the number is 5 or greater, the measurement is in millimeters.

The illustration on this page was made to demonstrate relative sizes of the various coins. For scale we have included a 19mm (AE19 if Greek, AE3 if late Roman) US cent.